Method of measuring unilateral flow rate of vehicles

ABSTRACT

The invention makes it possible to measure a lateral displacement amount of a vehicle accurately in a short time on a bench testing machine without damaging a vehicle body and tires.  
     Respective rollers  1 F,  1 R on which respective wheels WF, WR of the vehicle A are placed respectively are made movable in a lateral direction. In a state in which the respective wheels WF, WR are rotating at a predetermined speed, lateral forces (cornering forces) acting on the respective rollers  1 F,  1 R are detected by respective detectors 3. Then, a yaw angle speed when the vehicle A is brought into a state of steady circular turning is calculated based on the lateral forces acting on the respective rollers  1 F,  1 R and the lateral displacement amount is calculated from the yaw angle speed.

TECHNICAL FIELD

[0001] The present invention relates to a method of measuring a lateraldisplacement amount of a vehicle (a value indicating a distance by whichthe vehicle is displaced rightward or leftward while traveling areference distance) generated due to dispersions in assembly accuracy ofa vehicle body, accuracy of wheel alignment, and the like when thevehicle travels with its steering wheel in a straight-ahead state.

BACKGROUND ART

[0002] Conventionally, there is a known method as disclosed in JapanesePatent Application Laid-open No. 6-331505 in which a bench testingmachine having rollers for front wheels and rollers for rear wheels isused and the front and rear wheels of a vehicle are rotated on thecorresponding rollers to measure a lateral displacement amount of thevehicle. In this method, the bench testing machine is provided withadjusting wheels for coming in contact with the respective wheels of thevehicle from a lateral direction and load cells each for detecting aforce of each wheel pressing back each wheel in a lateral direction. Aninput load of the load cell when the wheel is rotated on the roller isconverted into the lateral displacement amount based on data showingcorrelation between a load cell input load and the amount of lateraldisplacement and collected by measuring the input load of a measuringapparatus and by measuring the lateral displacement amount in an actualtraveling test on a common vehicle in advance and an evaluation oflateral displacement on a pass/fail basis is conducted based on whetherthe lateral displacement amount is equal to or less than a referencevalue.

[0003] Conventionally, there is also a known method as disclosed inJapanese Patent Application Laid-open No. 8-43263 in which a benchtesting machine is provided with a swinging frame for moving back andforth in a lateral direction toward side sills of a vehicle and forswinging about a vertical axis, the swinging frame is mounted with apair of measuring rollers in contact with front and rear two positionsof the side sills of the vehicle, and a lateral movement amount and aswinging angle of the swinging frame are detected in a rotating state ofwheels and are respectively compared with each reference value tothereby conduct an evaluation of lateral displacement on a pass/failbasis.

[0004] In the former prior art, however, the data showing thecorrelation between the load cell input load and the lateraldisplacement amount need be obtained for each vehicle type, whichrequire much time and labor. Moreover, because the data are obtained bybringing the adjusting wheels into contact with side faces of a tire ofthe respective wheels, data values are affected by projections anddepressions on the side faces, true data cannot be obtained, andreliability decreases. Furthermore, contact marks may be left on thetires by the adjusting wheels which have come in contact with the tires.

[0005] In the latter prior art, translational motion of the vehicle inthe lateral direction is detected as the lateral movement amount of theswinging frame and yawing motion of the vehicle is detected as theswinging angle of the swinging frame. Even if the vehicle is displacedlaterally, much time is required for the vehicle to move laterally oryaw to such a degree as to be detected and it is difficult to measure ina short time. Moreover, because the measuring rollers are brought intocontact with the side sills, the side sills may be damaged.

[0006] With the above points in view, it is an object of the presentinvention to provide a method of measuring the lateral displacementamount of the vehicle accurately in a short time without damaging avehicle body and tires by using a bench testing machine.

DISCLOSURE OF INVENTION

[0007] To achieve the above object, according to the present invention,there is provided a method of measuring a lateral displacement amount ofa vehicle by using a bench testing machine including rollers for frontwheels and rollers for rear wheels and rotating the front and rearwheels of the vehicle on the corresponding rollers, the method includingthe steps of: making the respective rollers movable in a lateraldirection and detecting lateral forces acting on the respective rollersin a state in which the respective wheels are rotating at apredetermined speed; calculating a yaw angle speed of the vehicle whenthe vehicle is brought into a state of steady circular turning based onthe detected lateral forces on the rollers; and calculating the lateraldisplacement amount of the vehicle based on the calculated yaw anglespeed.

[0008] Movement of the vehicle when the vehicle is displaced in alateral direction is steady circular turning with an extremely largeradius. Here, the lateral forces acting on the respective rollers areequal to cornering forces of the respective wheels. The yaw angle speedcan be determined by substituting detected values of the lateral forceson the rollers as the cornering forces in an equation of motion at atime of the steady circular turning. The lateral displacement amount canbe calculated based on the yaw angle speed.

[0009] Therefore, there is no need to conduct an actual traveling teston each vehicle type and the lateral displacement amount can becalculated even if the vehicle does not move laterally or yaw to such adegree as to be detectable. Therefore, it is possible to shorten ameasuring time. Moreover, because measuring members need not be broughtinto contact with a vehicle body or tires, damage to the vehicle bodyand tires can be prevented, influence of projections and depressions onside faces of a tire can be avoided, and the lateral displacement amountcan be calculated with accuracy.

BRIEF DESCRIPTION OF DRAWINGS

[0010]FIG. 1 is a perspective view of a bench testing machine used forcarrying out a method of the present invention.

[0011]FIG. 2 is a flow chart showing a procedure for measuring a lateraldisplacement amount.

[0012]FIG. 3 is a diagram showing a model of motion of a vehicle.

BEST MODE FOR CARRYING OUT THE INVENTION

[0013]FIG. 1 shows a bench testing machine including a pair of right andleft front wheel rollers 1F, 1F on which right and left front wheels WFof a vehicle A are placed respectively and a pair of right and left rearwheel rollers 1R, 1R on which right and left rear wheels WR of thevehicle A are placed respectively. The respective front wheel and rearwheel rollers 1F and 1R are respectively formed of front and rear twodivided rollers 1 a, 1 a axially supported on respective roller supportframes 2F, 2R. The respective roller support frames 2F, 2R are supportedto be movable in a lateral direction along guide rails 2 a. Detectors 3such as load cells for detecting lateral forces acting on the respectiverollers 1F and 1R through the respective roller support frames 2F and 2Rare provided. Furthermore, speed meters 4 for detecting rotationalspeeds of the respective rollers 1F, 1R, a motor 5 for driving theroller 1R for the rear wheels WR which are follower wheels, and acomputer (not shown) to which signals from the detector 3 and the speedmeter 4 are input are provided.

[0014] In measuring a lateral displacement amount of the vehicle A, therespective wheels WF, WR of the vehicle A are placed on the respectivelycorresponding rollers 1F, 1R, the vehicle A is restrained by restrainingmeans (not shown) so as not to be displaced laterally, while a steeringwheel of the vehicle A is held in a straight-ahead position, the frontwheels WF which are driving wheels are rotated by a vehicle-mountedengine, and the rear wheels WR which are the follower wheels are rotatedat the same speed as the front wheels WF by the motor 5 through therollers 1R. Then, as shown in FIG. 2, immediately after the rotationalspeeds of the front wheels WF and the rear wheels WR have reached apredetermined speed V (e.g., 40 km/h in terms of a vehicle speed) (S1),the lateral forces acting on the respective rollers 1F, 1R are sampledby the respective detectors 3 for a predetermined period (e.g., 100msec) (S2).

[0015] Here, the lateral displacement of the vehicle A is a resultantmovement of lateral translational motion and yawing motion. FIG. 3 showsa simplified two-wheel motion model of a four-wheel vehicle. In thedrawing, reference numerals YF and YR designate cornering forces of thefront wheels WF and the rear wheels WR respectively, βF and βR designateside slip angles of the front wheels WF and the rear wheels WRrespectively, δF and δR designate toe-in angles of the front wheels WFand the rear wheels WR respectively, β designates a side slip angle of acenter of gravity of the vehicle A, ω designates a yaw angle speed ofthe center of gravity of the vehicle A, F designates a force of lateralmovement of the center of gravity of the vehicle A, L designates adistance between the front wheels WF and the rear wheels WR, LFdesignates a distance between the center of gravity of the vehicle A andthe front wheels WF, and LR designates a distance between the center ofgravity of the vehicle A and the rear wheels WR.

[0016] If the total cornering force of the right and left front wheelsWF is 2 YF and the total cornering force of the right and left rearwheels WR is 2 YR, an equation of the translational motion of thefour-wheel vehicle is $\begin{matrix}{{F = {{M \cdot {V\left( {\frac{\beta}{t} + \omega} \right)}} = {2\left( {{YF} + {YR}} \right)}}},} & (1)\end{matrix}$

[0017] where M is a vehicle weight. An equation of the yawing motion is$\begin{matrix}{{{I\frac{\omega}{t}} = {2\left( {{{LF} \cdot {YF}} - {{LR} \cdot {YR}}} \right)}},} & (2)\end{matrix}$

[0018] where I is moment of inertia around the center of gravity of thevehicle A. YF and YR are $\begin{matrix}{{YF} = {{{{- {KF}} \cdot \beta}\quad F} = {- {{KF}\left( {\beta + \frac{{LF} \cdot \omega}{V} - {\delta \quad F}} \right)}}}} & (3) \\{{{YR} = {{{{- {KR}} \cdot \beta}\quad R} = {- {{KR}\left( {\beta - \frac{{LR} \cdot \omega}{V} - {\delta \quad R}} \right)}}}},} & (4)\end{matrix}$

[0019] where KF and KR are tire cornering powers (constant valuesinherent in tires and determined by rim diameters, widths, and airpressures of the tires) of the front wheels WF and the rear wheels WRrespectively. In an initial state of the lateral displacement, ω=β=0 and

YF=KF·δF→F=YF/KF   (3′)

YR=KR·δR→R=YR/KR   (4′)

[0020] Substituting the equations (3) and (4) in the equations (1) and(2) and simplifying them yield $\begin{matrix}{{{{M \cdot V}\frac{\beta}{t}} + {2\left( {{KF} + {KR}} \right)\beta} + {\left\{ {{M \cdot V} + \frac{2\left( {{{KF} \cdot {LF}} - {{KR} \cdot {LR}}} \right)}{V}} \right\} \omega}} = {2\left( {{{{KF} \cdot \delta}\quad F} + {{{KR} \cdot \delta}\quad R}} \right)}} & (5) \\{{{2{\beta \left( {{{KF} \cdot {LF}} - {{KR} \cdot {LR}}} \right)}} + {\frac{2\omega}{V}\left( {{{KF} \cdot {LF}^{2}} + {{KR} \cdot {LR}^{2}}} \right)} + {I\frac{\omega}{t}}} = {2\left( {{{{KF} \cdot {LF} \cdot \delta}\quad F} - {{{KR} \cdot {LR} \cdot \delta}\quad R}} \right)}} & (6)\end{matrix}$

[0021] If the vehicle A performs steady circular turning, dω/dt=0,dβ/dt=0. Therefore, the equations (5) and (6) are $\begin{matrix}{{{2\left( {{KF} + {KR}} \right)\beta} + {\left\{ {{M \cdot V} + \frac{2\left( {{{KF} \cdot {LF}} - {{KR} \cdot {LR}}} \right)}{V}} \right\} \omega}} = {2\left( {{{{KF} \cdot \delta}\quad F} + {{{KR} \cdot \delta}\quad R}} \right)}} & \left( 5^{\prime} \right) \\{{{2\left( {{{KF} \cdot {LF}} - {{KR} \cdot {LR}}} \right)} + {\frac{2\omega}{V}\left( {{{KF} \cdot {LF}^{2}} + {{KR} \cdot {LR}^{2}}} \right)}} = {2\left( {{{{KF} \cdot {LF} \cdot \delta}\quad F} - {{{KR} \cdot {LR} \cdot \delta}\quad R}} \right)}} & \left( 6^{\prime} \right)\end{matrix}$

[0022] Then, from the equations (5′) and (6′), ω is determined asfollows.

ω=V(δF−δR)/(1−K)L   (7)$\left( {K = {1 - {{\frac{M}{2L^{2}} \cdot \frac{{{KF} \cdot {LF}} - {{KR} \cdot {LR}}}{{KF} \cdot {KR}}}V^{2}}}} \right.$

[0023] Substituting δF, δR of the equations (3′) and (4′) in δF, δR ofthe equation (7) yields $\begin{matrix}{\omega = {{{V\left( {\frac{YF}{KF} - \frac{YR}{KR}} \right)}/\left( {1 - K} \right)}L}} & \left( 7^{\prime} \right)\end{matrix}$

[0024] Here, if the lateral force acting on the roller 1F for the rightfront wheel is YFR, the lateral force acting on the roller 1F for theleft front wheel is YFL, the lateral force acting on the roller 1R forthe right rear wheel is YRR, and the lateral force acting on the roller1R for the left rear wheel is YRL,

YF=(YFR+YFL)/2   (8)

YR=(YRR+YRL)/2   (9)

[0025] Thus, by substituting the lateral forces of the respectiverollers 1F and 1R detected by the respective detectors 3 in theequations (8) and (9) to calculate YF and YR respectively andsubstituting YF and YR in the equation (7′), the yaw angle speed ω in astate in which the vehicle A performs steady circular turning can becalculated.

[0026] After the yaw angle speed ω is calculated from detected values ofthe lateral forces of the respective rollers 1F and 1R in the abovemanner (S3), the lateral displacement amount H of the vehicle A iscalculated based on the yaw angle speed ω (S4). Here, because thelateral displacement amount H is a distance of translational movement inthe lateral direction and a translational acceleration in the lateraldirection of the vehicle A is V(dβ/dt+ω), H can be shown as:$\begin{matrix}{H = {\int{\int{{V\left( {\frac{\beta}{t} + \omega} \right)}{t^{2}}}}}} & (10)\end{matrix}$

[0027] In the steady circular turning, dβ/dt=0 and the equation (10)becomes as follows: $\begin{matrix}{H = {{\int{\int{{V\omega}\quad {t^{2}}}}} = {{\int{\left( {{Ho} + {{V\omega}\quad t}} \right){t}}} = {{Ho} + {Vot} + {\frac{1}{2}{V\omega}\quad t^{2}}}}}} & (11)\end{matrix}$

[0028] H₀ and V₀ are initial values of the lateral translationaldistance and the lateral translational speed respectively. Because ofH₀=V₀=0 in the steady circular turning, H can be modified as:$\begin{matrix}{H = {\frac{1}{2}{V\omega}\quad t^{2}}} & (12)\end{matrix}$

[0029] If the lateral displacement amount H is used as a valueindicating a distance by which the vehicle is displaced in the lateraldirection while traveling 100 m, t must be:

t=100 (m)/V (m/sec)

[0030] and the lateral displacement amount H (m/100 m) can be determinedby substituting t in the equation (12).

[0031] As is apparent from the above description, according to theinvention, the lateral displacement amount of the vehicle can bemeasured accurately in a short time on the bench testing machine withoutdamaging the vehicle body and the tires to increase efficiency.

1. A method of measuring a lateral displacement amount of a vehicle byusing a bench testing machine including rollers for front wheels androllers for rear wheels and rotating the front and rear wheels of thevehicle on the corresponding rollers, the method including the steps of:making the respective rollers movable in a lateral direction anddetecting lateral forces acting on the respective rollers in a state inwhich the respective wheels are rotating at a predetermined speed;calculating a yaw angle speed of the vehicle when the vehicle is broughtinto a state of steady circular turning based on the detected lateralforces on the rollers; and calculating the lateral displacement amountof the vehicle based on the calculated yaw angle speed.